1. Field of the Invention
The present invention relates to an image forming system such as an electrophotographic copier, printer, facsimile, or an inkjet printer and a sheet feeder installed in the image forming system to feed a recording sheet.
2. Description of the Related Art
In an image forming system such as a copier, a sheet feeder such as a sheet stacker that loads therein paper, onto which an image formed on an image carrier (e.g., a photosensitive element) is to be transferred and fixed, is typically configured to be adjustable to diverse sheet sizes.
Such a sheet feeder typically includes a side fence for regulating side ends of sheets to inside the fence. The side fence is typically slidable to be adjusted to the width of loaded sheets.
Among such sheet feeders, a sheet feeder having a large sheet loading capacity of, e.g., 2,000 sheets or more, includes a paper loading section that is high enough to load such a large number of sheets therein. The height of the side fence that regulates side ends of the sheets to inside the fence of this sheet feeder also depends on the number of sheets of the maximum loading capacity.
The side fence is arranged at each of opposite side ends of the sheets. A rack is attached to a bottom end of the side fence, and a pinion to be meshed with the rack is provided. When one of the side fences is caused to slide, rack-and-pinion gearing causes the other side fence to also slid. The side fences position the sheets by sandwiching the sheets therebetween from the opposite side ends in this way.
Each of the side fences further includes a guide member that guides a sliding direction of the side fence.
A technique related to this type of sheet feeder is disclosed in Japanese Patent No. 3906886, for example. According to this technique, as illustrated in FIG. 16, a bracket 102 is arranged on a top portion of a side fence 101 and moves in synchronization with the side fence 101. Thumbscrews 104 that fasten the bracket 102 and a sheet stacker 103 are tightened to lock the side fence 101 at a desired position.
Another technique related to this type of sheet feeder is disclosed in Japanese Patent No. 4241528, for example. According to this technique, as illustrated in FIG. 17, guide shafts 205 arranged in bottom portions of side fences 201 and fixed to a sheet stacker 203 are locked with a scheme that uses locking couplings (not shown) that are attached to the side fences 201 so that the side fences 201 are locked at desired positions.
However, the technique disclosed in Japanese Patent No. 3906886 requires a user, when loading sheets, to remove a plurality of thumb screws attached to the side fences, adjust the side fences to side ends of the sheets, and then refasten the plurality of thumb screws. Accordingly, this technique is disadvantageously less convenient because it involves the trouble of refastening the thumb screws.
According to the technique disclosed in Japanese Patent No. 4241528, the side fences are fixed at basal end portions of the side fences. Accordingly, the side fences are not fixed at their top portions. When the side fences possess low rigidity, a clearance between the side fence and a sheet can be undesirably created at a position near a top surface of a sheet stack from which a sheet is to be delivered. This can result in skewing of the sheet during sheet feeding or the like.
Therefore, there is a need to provide a sheet feeder that can properly regulate side ends of sheets to within a given range.